S7 Check Sequence Msg

Hello when I download the blocks in S7 I get a msg from SIMATIC which is:

"Check the sequence of the blocks that is required for the correct function"

This happened out of nowhere and when I click OK the system goes on downloading and no problem occurs. Has anyone met this situation before? Why this happens? Thanks

It happens every time you download more than one block.

It is just a reminder to be extra careful that you dont mess things up. In some cases, the sequence that the blocks are downloaded makes a difference.

I believe that the downloaded blocks remain inactive until the last one has finished downloading, and then the PLC activates the downloaded blocks in one go (neat feature methinks). However, if there is not enough spare memory, this wil not work and some of the blocks will not be downloaded before some others go active. This may or may not be a potential problem.
Notice that the blocks get downloaded in the order that you select them in Simatic Manager (also a neat feature).